Patients newly diagnosed with breast cancer face a series of complex decisions regarding locoregional and systemic treatment. Currently many of these decisions do not meet the definition of a high quality decision, defined as one that is both informed (i.e., based on an accurate understanding of the treatment risks and benefits) and preference-concordant (i.e., consistent with the patients' underlying preferences). Moreover, the introduction of evaluative tests has made these decisions more complicated for many patients. There is a need to improve the quality of locoregional and systemic treatment decisions for breast cancer patients, and to help patients understand the role of evaluative tests in this decision process. Ensuring patients can deliberate effectively about these decisions, assert their views and communicate with their clinicians is likely to improve their overall decision preparedness and satisfaction. Project 3 will focus on the third pillar of individualized care by evaluating the impact of an innovative decision tool on locoregional and systemic therapy decision making for newly diagnosed breast cancer patients. The innovative online decision tool has been developed and tested over the past two years by the CanSORT team (R21 CA129859). Pilot data suggests that this tool has a positive impact on patient knowledge and decision outcomes. The goal of project 3 is to evaluate the impact of this tool, after it is enhanced in collaboration with our Communication and Dissemination Core, on the quality of decision making for locoregional and systemic breast cancer treatment decision making. We will conduct a randomized controlled trial (RCT) of 444 newly diagnosed patients with invasive early stage breast cancer, seen by 28-30 surgeons in two SEER catchment areas. Patients will be randomized to view our comprehensive decision tool or a state of the art existing website. The primary outcomes will be the rate of high quality decisions about locoregional and systemic therapy for patients viewing the CanSORT tool vs. the existing website. Additional outcomes will include patient knowledge about evaluative tests and the extent of decision deliberation. The results of this RCT will be highly relevant to future breast cancer patients making these decisions and to their clinicians.